For
all that we mock the traditional publishing industry, any book that
makes it through that process has gone through many quality filters.  If
you further limit yourself to books that have withstood the test of
time, reading books is the best way to inject concentrated, high-quality
knowledge into your brain.

Step 2: Write up your notes each time you finish a book.

Consolidate
your knowledge by writing your own summary afterwards.  1) This action
“fixes” the knowledge in your brain.  2) You can always refer back to
your summary afterwards to refresh your knowledge, and since you wrote
it, it will be uniquely accessible to you.

You can find a lot of the books I’ve read here:
The Book Outlines Wiki

For
example, I recently read a book on coaching, counseling, and mentoring
to help me in my own executive coaching practice; taking notes will help
me retain and apply what I learned:
Coaching Counseling and Mentoring